Peripheral administration of a rho-associated protein kinase (ROCK) inhibitor is capable of improving learning and working memory in an aged rat. Myristoylated alanine-rich C-kinase substrate (MARCKS) is one of the downstream targets of the RhoA/ROCK pathway and is known to participate in several key neuronal cell functions including neurite outgrowth and growth cone adhesion. SH-SY5Y cells stimulated with increasing doses of insulin-like growth factor (IGF-1) demonstrated a both significant and rapid decrease in phosphorylated MARCKS, and a significant increase in the number of neurite bearing cells. Additionally, memory formation occurs when neurons grow and make new connections. Therefore, inhibitors of MARCKS are needed as enhancers of memory. In addition, an association between the MARCKS protein and Alzheimer's disease (AD) was suggested. Phosphorylated MARCKS was detected in the 3-Amyloid plaques of human hippocampal and parahippocampal brain tissue sections. Therefore, MARCKS' presence in the neuropathology of AD suggests a likely connection of MARCKS to AD.